The LRM-5 is the smallest and lightest of the Long Range Missile family. Its light weight and small size give even small 'Mechs the ability to strike at range. Each missile does 1.1 points of damage. All LRMs have a minimum range where their warheads have insufficient time to arm after firing. An LRM's minimum range is 180m, below which the damage very rapidly decreases to nothing at point blank range.
The Artemis IV FCS upgrade increases the tracking strength and decreases the lock down time by 50%. However, each launcher requires an extra critical space and 1 extra ton for the Artemis control system this makes Artemis on multiple smaller launchers less tonnage efficient than on a single larger launcher.
While ECM makes the effective use of LRMs slightly more difficult, it is possible. If you are alone with an ECM equipped foe, staying within 181 and 200m will allow you to use your weapons with lock. If you have a TAG spotter, as long as they are at least 181m from the target and maintain the tag on the target, you will have your target. If you have a PPC spotter, you have your target as long as they keep the ECM disabled.